When choosing a replacement gas boiler or for your new home consider choosing a condensing version; it will lower your running costs considerably. The efficiency comes from the boiler being able to extract the heat in the flue gas that is otherwise sent through to atmosphere and wasted. The boiler captures this heat and uses it to preheat the combustion air and gases to be burnt resulting in higher efficiency up to 25% more efficient than an equivalent non-condensing boiler. They will also have lower emissions of carbon dioxide. The brand of boiler we frequently install is Volkera with an extensive warranty.
Non-condensing boilers are in New Zealand because we, unfortunately, buy them as an unregulated market. In overseas markets they are not allowed to sold and in some cases like the UK since 2005. New Zealand has been a bit of a dumping ground for lower grade product for a number of years now.
There are several models and styles of efficient condensing boilers. Some called Combi boilers have capacity to provide on-demand hot water similar to a Rinnai Infinity that are capable of up to 24 litres per minute. These Combi Boilers can heat your domestic supply for homes with up to 2 bathrooms and also run your underfloor heating.
Efficient condensing gas boilers have a multitude of uses from domestic water heating through to whole home heating solutions including underfloor heating and radiator systems. Very effective in all areas and low running costs running using natural gas. LPG is efficient but has a higher cost per kilowatt than natural gas.
For larger homes it is recommended to use a buffer tank with a gas boiler for recovery. These buffer tanks or Multi Energy Source Cylinders have internal heat exchanger coils and are able to supply a larger home with more bathrooms. The Multi Energy Source Cylinders can also have a solar system installed for even further increased efficiency.
Hot Water Heat Pump (HPHW)
HPHW Has been around for at least the last 40 Years. With new branding and the latest technology they have evolved into a very efficient heat source, Air Source HPHW is a good option in our Bay of Plenty region because the ambient air temperature does not often go below 11 degrees.
HPHW suits tasks where high temperatures of water are not required but there is one exception (will get to that in a minute). HPHW generally work on very high efficiency till the water gets to 40 degrees Celsius, then the heat requirement input increases per degree requiring more energy with every degree to be heated, to extract maximum efficiency from HPHW suitable tasks revolving around lower temperature hot water are Underfloor Heating, Radiator Heating is possible on a smaller home with aluminium Radiators, and Pool or Spa heating. All of these options require careful sizing and calculation to have the right product for the job. With careful system design it is possible to gain great Efficiency up to 400%.
The exception for heating water above 40 degrees Celsius as mentioned earlier is the Econergy hp4000 HPHW. This is a domestic supply only hot water system capable of great efficiency. There are a few imported brands offering good savings of power usage, however the Econergy hot water heat pump has been tested and proven to be the most efficient, offering 70% savings on heating, where some brands are only at 50%.
www.econergy.co.nz. Hot water heat pumps offer straight line performance all year round and offer savings for high water user families with small or large HWC where solar cannot run efficiently. These systems offer maximum convenience at lowest running cost; able to heat 70 litres of hot water to full temperature of 62 degrees per hour at lowest running cost possible. When the system is on standby no power is used.
These running costs do vary depending on which power company you support and whether on controlled power or not.
The ECONERGY heat pump is able to be fitted to new installations and retrofitted to existing hot water systems. ECONERGY is a quality New Zealand made product. Advantages for an ECONERGY are low installation costs, no building consent required, flexible appliance locations and able to run on ripple control.
We have made many happy clients from fitting the ECONERGY in our region and they suit people with families who use a lot of hot water. The reason for this is that it works on a thermostat and when required on demand at the same high efficiency, whereas with solar when your tank of water is used up the electric boost element kicks in, this is why small hot water cylinders do not suit solar applications.
Solar hot water heating as a Heat source has generally been over promised and oversold. The promises made by salesmen in our area in past times goes beyond the capability of physics and are an embarrassment to the industry.
However, if sized correctly like all other systems they offer very good performance. The hot water cylinder is the key to good solar performance and a good controller. The HWC acts as a thermal store or Battery – the larger the battery the more energy you can store. This is why 180 litre HWC or smaller really are not the most efficient use for solar. EECA made a study a few years ago and proved that for a domestic use home the most efficient size was 300 litres. If the solar system is matched to the correct HWC size or capacity savings of up to 75% are easily possible equating to most of the year not requiring any Electrical back up to heat the water to sanitary temperature level.
A typical standard system rated for a 300 HWC is rated at 2.8kw/hr on a yearly basis, a smaller system capable of heating 180 hwc is rated at 1.8kw/hr. With solar quality is everything and don’t be trapped into getting super cheap unsupported product from Trademe or disreputable importers from China.
Solar is also good for pool heating but requires careful design to get the collector size and ration to pool surface area correct
There are systems that will do underfloor heating however they are very large, they will require a large thermal store up to 1000 litres and the solar system on roof occupies a large space, with all the heat generated there is requirement is summer to use all the unwanted excess energy; the most convenient method would be pool heating. The costs involved are over $35 000.
To recap solar is very useful and still efficient heat source but requires careful design for the task at hand.